Comment on attachment 326656[details][diff][review]
Patch
Yeah, either wait for Moz2 (and re-request reviews then), or create a new nsIDOMNSHTMLLinkElement interface that extens nsIDOMHTMLLinkElement and adds this property.

The IDL attribute shouldn't be a DOMString but a DOMSettableTokenList.
By the way, if you just need .sizes done this way (a simple reflection of the content attribute), you can use .getAttribute('sizes') for the moment and change that when .sizes will be implemented.

Comment on attachment 480604[details][diff][review]
corrected patch
Mounir is very true.
.sizes isn't a DOMString, but DOMSettableTokenList.
Unfortunately the current HTML5 draft has [PutForwards=value] -
I think we should get rid of that.
Want to sent question to whatwg why Hixie has used
PutForwards (which is generally an indicator of an ugly API, IMHO)?